1. Field of the Invention
The invention relates generally to an apparatus and method for manufacturing a magnetic core of a toroidal transformer and, more particularly, to an apparatus and method for manufacturing a wound magnetic core of a toroid transformer with an R-angle.
2. Description of the Related Art
A transformer is an electrical device used to provide a low-voltage power supply from a high-voltage alternating-current (AC) power source, or a high-voltage supply from a low-voltage AC power source. In its most basic form, a transformer consists of a primary coil connected to an AC voltage source for receiving energy therefrom, a secondary coil connected to a load for receiving energy from the primary coil and transmitting to the load, and a core supporting the coils for providing a path for the magnetic lines of flux. The magnetic field (flux) builds up (expands) and collapses (contracts) about the primary coil. The expanding and contracting magnetic field around the primary coil cuts the secondary coil and induces an alternating voltage into the coil. This voltage causes alternating current to flow through the load. The voltage may be stepped up or down depending on the design of the primary and secondary coils.
Transformers are frequently classified on the basis of their uses and purposes, whereas the detailed constructions of the transformers depend on the intended application. Power transformers are generally used to transmit power at a constant frequency. Audio transformers are designed to operate over a wide range of frequencies with a nearly flat response, i.e., a nearly constant ratio of input to output voltage. Radio frequency (RF) transformers are designed to operate efficiently within a narrow range of high frequencies.
Transformers often include silicon steel cores to channel the magnetic field. Such cores keep the magnetic field more concentrated around the coils so that the transformer is more efficient. The cores also keep the magnetic field from being unnecessarily wasted in adjacent pieces of metal. A commonly available transformer core is the toroid core. A toroid transformer is made by placing coils around a core having a closed annular form. The toroid core can be made from magnetic metal alloy by casting, by lamination from magnetic metal alloy sheets, or by winding from a continuous magnetic metal alloy ribbon.
According to a method and apparatus in the art for manufacturing a wound toroidal transformer core, a continuous ribbon of annealed amorphous magnetic core material is removed from a supply spool and wound into an annular cavity defined by a rotating bobbin within a partially assembled toroidal transformer. Efforts are accordingly made to prevent the varnish coating on the coils from being damaged during the subsequent coil winding process. Typically, a lathe machine will be utilized to grind the radial corners of the wound core into an R-angle such that the coils are wound more tightly and uniformly onto the wound cores, as opposed to those without an R-angle.
However, since the inner and outer diameters of the wound toroidal cores are generally different, a set of clamping devices for accommodating different sizes of the wound cores are needed in advance for the lathe machine for securely clamping the wound core. Such disadvantageously makes the manufacturing process unduly burden some significantly increase the cost of the manufacturing equipments. In addition, small particles, which come off the wound core during the lathing process and enter into spaces between layers of the wound core material, become independent conductors that adversely affect the magnetic lines of flux therein. Moreover, iron loss is significantly increased due to damage on the insulating layers of the radial corners of the wound cores.
There is thus a general need in the art for an optimally designed and implemented wound magnetic core for a toroid transformer that advantageously overcomes at least the aforementioned shortcomings in the art.
In view of the above problems in the art, a primary object of the invention is to provide an apparatus (with a corresponding method) for manufacturing a magnetic core with an R-angle, which advantageously reduces the copper loss, saves the coil material and increases the yield of the toroidal transformers including a wound toroid core thus formed.
The invention accordingly provides an apparatus for manufacturing a magnetic wound core with an R-angle, comprising a control device for controlling the apparatus based on parameters of the core material and the wound core, a supplying device for providing the core material ribbon, a grinding device for grinding the lateral edges of the core material ribbon under the control of the control device, and a winding device for receiving and winding the core material ribbon into the wound core.
In an embodiment of the invention, the apparatus for manufacturing a magnetic wound core with an R-angle further comprises a calibration device for keeping the core material leaving from the supply device horizontally and centered, a counting device for measuring the length of the core material passing therethrough, a punch device for cutting the core material ribbon into a predetermined length, a selecting device for directing the core material of a predetermined length for disposal if the length of the core material ribbon is not the predetermined length and a unloading device for taking the wound core out of the winding device.
In accordance with a further embodiment of the invention, a method is advantageously provided for manufacturing a magnetic wound core having an R-angle from a core material ribbon. The method according to this particular embodiment comprises the steps of cutting the core material ribbon into a predetermined length, forming the core material ribbon having lateral edges into a spread-out shape (such as a generally trapezoidal shape), grinding the lateral edges of the core material ribbon, and winding the core material ribbon into the core wound.